feat(tenant/articles): aggregate publish status from per-account records

a.publish_status only stored a coarse summary so the article list/detail
mis-reported as 失败 when one of several accounts failed. Compute the
effective status via a LATERAL join over latest publish_records per
platform_account_id and bucket into success / publishing / failed /
partial_success. Wire the same expression into list filtering and detail
queries, and let normalizePublishStatus / batch-status helpers retain
partial_success end-to-end.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/app/media_service.go

@@ -154,6 +154,8 @@ func normalizePublishStatus(status string) string {
 	switch status {
 	case "success", "published", "publish_success":
 		return "success"
+	case "partial_success":
+		return "partial_success"
 	case "publishing", "pending", "queued", "running":
 		return "publishing"
 	default: